This guide on ‘How To Rebuild Motorcycle Brake Calipers’ is here to give you useful hints and tips to sucesfully rebuild your brake calipers! After reading this guide, if you still feel unsure- Get in Touch! we have a specialist workshop and offer brake caliper rebuild services. We also have a video available here showing you how to rebuild brake calipers step by step.
How To Rebuild Motorbike Brake Calipers
Before Removing the Calipers From The Bike.  With the brake pads removed, use the brake lever to pump your pistons out towards the brake disc (you can protect the disc with cardboard if required). If any are stuck, use penetrating oil and leave for 30 minutes; if the pistons are still seized warm the caliper with a hot air gun. If the pistons are stuck after this, you may need special tools. Or see our Brake caliper Rebuild services. On jointed calipers, initially ’crack’ open the joint bolts while still mounted to the bike.
Piston Removal. If you don’t have specialist piston removal tools, take great care not to damage the pistons. You can use various types of grips or a vice, but line the jaws with rubber, lead or aluminium sheet if gripping the outside of the pistons to protect them. If the pistons do get damaged, we have replacements available in our shop.
Corrosion Removal. This is where most people get it wrong! Be sure to remove all dirt and corrosion from the seal grooves with a blunt scraper and/or a brass Dremel brush. This is very important – Alot of people try to use brake cleaner and a tissue, this just isn’t hard enough on the aluminium oxide!
Faliure to follow this step correctly will result in; the seals binding on the brake pistons, the seals leaking (as they will not be seated correctly), the potential damage of the seals whilst trying to fit the pistons.
So please take care at this step before moving forwards!
On the pistons, there may be a small amount of corrosion which can often be cleaned using a scotchbrite pad or similar, but if there is any pitting, or damage is present on the piston where the seals contact, they will need to be replaced. We have stainless steel pistons available in our shop.
The careful preperation of the caliper is always the part of the service which takes the most time. Once all of the corrosion is cleared from the seal grooves and the deadbris has been cleaned out of the caliper, and with the pistons either cleaned to a satisfactory condiiton, or replaced then you are ready to rebuld the brake caliper!
Fitting Seals. The Brakemastersâ„¢ seals are square section and not tapered so can be fitted either way up. Seals may seem loose if placed over the pistons when not in the caliper – this is normal. Once they are constrained in the seal groove within the caliper bore, they will be a perfect fit.
External dust boots and slide rod boots when new can appear small in comparison to the old parts – this is also normal. The old parts can swell to almost twice their normal size with age and exposure to cleaning chemicals, etc.
When fitting the seals use a thin smear of rubber grease or brake fluid to lubricate the seals and then the same for the pistons, align the pistons carefully in the bore and use only thumb pressure to ease the pistons past the seals to avoid pinching and damaging the seal.       Do not force the pistons in, if they are stiff check again that the seal grooves are totally clear of corrosion before continuing.
Bleed Screws. Ignore Kawasaki and Suzuki recommendations for 7.5-7.8 Nm torque on 7mm bleed screws – this is close to shearing the screw. Honda and Triumph only recommend 6 Nm for the stronger 8mm bleed screws. About 4 Nm is usually plenty for 7mm bleeds – only turn far enough to seal and no more.
Bleeding. With dry rebuilt internals brake calipers can be harder to bleed. We recommend:
1 – Open bleeds and allow gravity feed until fluid shows at each bleed.
2 – Quick lever pumping with bleed open one side at a time will purge most air.
3 – Tap down the brake lines to dislodge any trapped air bubbles.
4 – Slow ‘open bleed/squeeze/close bleed/release’ to remove the last air bubbles.
Keep reservoir full. If necessary, leave overnight to settle and final bleed the following day
Still feel unsure and want peace of mind? Find out about our in-house Brake Caliper Rebuild Services
Feel like your calipers need a recoat? Our Refurbishment Service is for you.
Rebuilding my calipers sounds great, but where do I buy the parts? Visit either our Online Shop Or Our Ebay Store
Last but not least, for more information or advice – Contact us!
We also offer ECU Remapping on cars – Economy & Performance options available.
The above video features the Brakemastersâ„¢ GSX1400 front brake caliper piston & seal kit. We also stock the front seal kit (without pistons), and the rear caliper seal kits with and without pistons.
